The disclosure relates to bond pads on a suspension tail for hard disk drive head stack assemblies.
Information storage devices are used to retrieve and/or store data in computers and other consumer electronics devices. A magnetic hard disk drive is an example of an information storage device that includes one or more heads that can both read and write. A contemporary trend is to include more devices in and on the head, e.g., a head stack assembly, which may facilitate reading and writing (for example, a heater to reduce head-disk spacing during reading or writing), and/or perform other functions such as micro-actuation or lapping control. As more devices are included in and on the head, the number of electrical connections to the head must increase.
Each of the read/write heads are controlled by signals transmitted to and from the heads through traces on a corresponding suspension flexure. The traces on the suspension flexure are bonded to the head at appropriate corresponding bonding pads. A typical approach to joining the traces on the suspension flexure to the head may be solder jet bonding.
A conventional suspension bond pad rests on polyimide base. Typically, there is a continuous layer of polyimide between the traces at the points of solder jet bonding. Two disadvantageous effects may occur, e.g., solder bridging across the polyimide between adjacent traces may occur, and the polyimide may incur burning as a result of the soldering, introducing contaminants in the bonding region. Solder bridging and burning during solder jet bonding (SJB) may result in a high level of defects. Most burning defects may occur at the polyimide base beside the suspension pad at the bottom half of the suspension pad length. There is a need, therefore, to find a solution that improves yield in solder jet bonding between suspensions and sliders in hard disk drive head stack assemblies.